This is a multicenter, randomized, double-blind trial of ZDV (180 mg/m2 q6h) versus ddI (120 mg/m2 q12h) versus a combination of ZDV and ddI (ZDV 120 mg/m2 q6h plus ddI 90 mg/m2 q12h) to evaluate the safety, tolerance and efficacy of the treatment arms. All drugs will be administered orally.